Combined thermal-magnetic circuit breaker



Patented June 14, 1949 COMBINED THERMAL-MAGNETIC CIRCUIT BREAKER Kurt Dannenberg, Stoke-on-Trent, England Application November 13, 1943, Serial No. 510,180 In Great Britain November 13, 1942 13 Claims.

Cartridge fuses have a. distinct tendency to protect circuits against light fault currents but from a service point of view this is undesirable as the occurrence of light overloads, which are usually of a transient nature, does not merit the blowin of the fuse.

The primary object of the present invention is the provision of an electric cut-out comprising a .it is desired t render the said fusible element immune, and trip gear normally held set, said fusible element being adapted when operated to displace a striker and said overload protection device being adapted when operated to displace another striker and said strikers being commonly associated with the trip gear so as to upset it by operation of either. When the cut-out is in the circuit to be protected, the trip gear being adapted when upset to operate or to bring about the operation of a switch directly or indirectly controlling the circuit, currents in excess of the maximum value of the predetermined light overload range or light or transient overload currents of predetermined value upset. the trip gear and the latter operates the control switch to interrupt the circuit. The. said light or transient overloads I do. not, however, blow the. fuse. Under excess currents the overload protection device of the cut-out is preferably inoperative. That is, the cartridge fuse becomes effectively responsive prior to the effective response of the overload protection device, which is slower acting than said cartridge fuse in response to. fault currents in overload ranges. of. higher magnitudes.

A cut-out according to the invention may have the fusible element with striker and the overload protection device with striker triplicated, each pair (a fusible element and an overload protection device) being adapted to be connected to a separate phase of a three phase circuit and all pairs being commonly associated with the trip gear. The trip gear of such a cut-out when in use. is arranged to controlthe phases of a threephase. switch. or isolator in such a manner that trip gear release by the'operation of the fuse or the protection device in any pair operates the trip or the equivalent of the three-phase switch whereby two phasing on the uninterrupted phases is avoided in the event of a heavy overload occurring. Preferably, the cut-out incorporates means whereby the trip gear, when upset, is locked against re-setting so that the three-phase switch cannot be reclosed until an intact fusible element is substituted for the operated fusible element. A cartridge fuse provided with a striker adapted to open a three-phase switch and provided with locking means preventing closure of the switch before substitution of an intact cartridge fuse is described in my U. S. Patent No. 2,330,690 but the differences between this arrangement and that according to the present invention are readily apparent. The fusible element in the present invention is preferably comprised in a cartridge fuse, however, and a suitable fuse is that described in my said patent.

The overload protection device may be of any suitable kind wherein a mechanical movement is produced when a fault current is impressed on it. Such a device may comprise a thermal relay, a no-volt release coil, a trip coil, a bimetal element (of strip or coil form) or any other suitable overload protection device well known in the art. These devices are frequently automatically re-setting. Expansion or distortion of the bimetal element if used may release'a spring-loaded trip with a time delay dependent on the magnitude of the fault current to be dealt with and the heating effect thereof on the bimetal element. This said spring-loaded trip preferably comprises a striker which on operation travels a predetermined distance and is then looked.

The overload protection device and the fusible element may be located in a common insulating sheath or case, the sheath or case having ferrules, end tags or the like. The case may have suitable conducting leads, the lead-in being attached to the mounting tag or the like and the lead-out being in the form of a tag or the like representing a main connection to the cartridge containing the fusible element.

Three ways of carrying out the invention will now be described with reference to the accompanying drawings wherein:

Fig. I is a sectional side elevation of a cut-out unit, comprising a plunger in the trip gear, an end of said plunger being accessible externally of. the. casing of theunit;

Fig. 2 is a sectional side elevation of a cut-out unit comprising an auxiliary switch adapted to 3 be operated by trip gear comprising oscillatory members;

Fig. 3 is a front elevation of a cut-out unit comprising a rotatable shaft in the trip gear, said shaft being accessible externally of the case of the unit; and

Fig. 4 is a sectional side elevation of part of the unit shown in Fig. 3.

Each unit shown comprises a cartridge fuse I, an overload protection device 2 such as a trip coil, thermal relay or the like in series with the cartridge, said cartridge having connecting tags 3 at its ends and a striker 4 at one end and said trip coil or the like having connecting tags 5 at its ends and a striker 6 at one end. The cartridge fuse is preferably as described in my U. S. Patent No. 2,330,690 whilst the trip coil or the like is of a kind well known in the art and includes a striker lockout similar to that of Fig. 4 illustrated in this patent. The strikers 4 and 6 in each case move in like directions when their respective devices operate; in Figs. 1 and 2 the said strikers are in alignment and in the unit according to Figs. 3 and 4 they are parallel.

In Fig. 1 the cartridge I and the device 2 are secured by studs I to the bottom of an insulating casing 8 having an insulating cover 9. A tag 3 on the cartridge extends through one end of the casing 8 whilst a tag 5 on the device 2 extends through the opposite end.

The trip gear, Fig. 1, comprises two parallel links 93, I!) lying at right angles to the axes of the strikers 4 and 6, respectively. The links are supported at their upper ends by pivots I I mounted on the sides of the casing; pivots I2 at the bottoms of the links connect the latter to a rod I3. Near the top of the casing and parallel with the rod l3 and the strikers is a plunger I4. One end of the plunger lies within a cylinder I5 secured to an end of the casing by a screw and nut It and within the casing and between a flange I"! on the plunger and the fixed end of the cylinder is a spring I8. The plunger extends from the cylinder to and beyond the opposite end of the casing, said plunger being squared at this end at is and the squared part lying within a hole of like shape in the casing end, whilst the plunger beyond the squared part is screw threaded for the reception of an insulating head 20. The plunger has a laterally projecting pin 2| and a cam or catch 22 rigid with one of the links I0 lies in front of the pin so as to hold the plunger in a position to keep the spring I'I compressed. The squared part I9 of the plunger in co-operation with the hole of like shape in the case prevents rotation of the plunger when the head is screwed on and when the plunger is held by the cam in the position shown. The members III, I3, i4 and I8, with their associated parts, comprising the trip gear are shown in the set position.

The unit is fixed in its position of use, and is electrically connected to the circuit to be protected by means of the externally accessible parts of the tags 3 and 5. The externally accessible head 2! is located adjacent a switch diagrammatically shown at 23.

Overload currents within the range of the device 2 causes the latter to move its striker 6 outwardly and relatively heavier fault or short circuit currents cause operation of the fuse I prior to the effective response of the device 2, whereby the fuse I displaces its striker 4 before the striker 6 can become actuated. In either case the cam 22 is turned clockwise to free it from the pin 2| whereupon the spring I8 thrusts the plunger I4 to the left so that the head 20 closes the switch 23. The switch is associated with the main switch of the circuit in known manner and when closed causes the main switch to open.

In Fig. 2 the cartridge I and the device 2 are bolted to bars 24 extending across the insulating casing 25, said bars being suitably fixed to the sides of the casing. The casing is closed by an insulating cover 21.

The trip gear, Fig. 2, comprises two parallel links 28 lying at right angles to the plungers 4 and I3, respectively. Each link is supported between its ends by a shaft 23 mounted on the sides of the casing and is pivotally connected at 30 to a rod 3i. The upper link 23 is rigid with its shaft 25? and also rigid with the shaft is a catch 32. A tension spring 33 normally holds the parts 28, 3i and 32 in the position shown. The catch normally engages a detent 34 on a bell crank lever 35, the pivot 36 of which lever is carried by the sides of the casing. One arm of the lever 35 is attached to a tension spring 31 tending to turn the lever anti-clockwise but such turning movement is normally prevented by engagement of the detent with the catch. The other arm of the bell crank lever is connected by pin and slot means 38 to the operating arm 39 of an auxiliary switch 40 in the casing.

Operation either of the cartridge I or of the device 2 and resulting movement of a plunger (4 or 5) causes the links 28 to turn and the catch 32 to release the detent. Thereupon the spring 31 turns the lever 35 and the latter turns the switch arm 39.

In Figs. 3 and 4 the cartridge I and the device 2 are secured to insulating bars 4i bolted to lugs 43 at the sides of a metal casing 44, said casing having a cover 45.

The members I and 2 are parallel. The trip gear comprises a transverse plate 46 lyingabove the strikers 4 and 6 which plate has lugs 41 at its front rigidly securing it to a supporting shaft 48. One end of the shaft is carried by a bearing 49 at a side of the casing and the other end of the shaft, after passing through a bearing hole in a bracket 59 (Fig. 3), passes through and beyond a hole in the opposite side of the casing, a finger or re-setting lever 5| being secured to the projecting end of the said shaft. A catch 52 is fixed to the shaft 48. A tension spring 53 secured to the back of the casing and to an arm 54 rigidly upstanding from the shaft 48 normally holds the parts 46 and 52 in the position shown. The catch 52 engages with a detent 56 on a lever 51, said lever being fixed to a shaft 58 borne by the bracket 50 and a side of the casing, and a tension spring 59 attached to the outer end of the lever tends to turn the lever and the shaft 58 anti-clockwise. It will be seen that the shaft extends from the side of the case so as to be accessible externally of the said case.

Operation of either member I or 2 causes upward movement of a striker. The operated striker turns the plate 45, the shaft 48 and the catch 52 whereupon the catch is released from the detent. The spring 59 is then able to turn the lever 57 and the shaft 58, the turning movement of the shaft 58 being used to operate a control switch in any suitable manner.

The springs I8, 37 and 59 bringing about What may be termed the power movement of the trip gear may be selected to give the required degree of sensitivity of the tripping action. Moreover, owing to the fuse and the device 2 being associated with common trip gear it is possible to use in the same apparatus a fuse and a device 2 having greatly differing force ratios which forces, however, result in the release of a constant force available at the members displaced by the springs i8, 31 and 59.

The fuses and/or the devices 2 may be provided with looking devices preventing return of an operated striker as explained and shown in the aforementioned U. S. Patent No. 2,330,690, and/ or the trip gear may be provided with locking means preventing ready re-setting thereof after operation, see Figure 1. In this figure the reset plunger [4 is formed with an annular groove or recess adapted to receive a spring loaded locking bit 6| pivoted to the inner wall of case 8, as shown in Fig. 4 of U. S. Patent No. 2,330,690, when the plunger I4 is released and kicked outward by-the spring I8 as previously described in connection with Figure 1 of the present application.

It will be seen that the various parts of the units, with the exception of a tag 3, a tag 5 and an end of the plunger M, Fig. 1, and part of the shaft 58 and the re-setting lever 51, Fig. 3, are enclosed in the casings. The external accessibility of parts of the plunger l4 and shaft 58 enable connection to be made in any suitable manner to a distant switch.

A fuse cartridge and a device 2 may be arranged in a porcelain housing or the like for insertion into a metal case provided with trip gear.

The cartridge fuse in the cut-out herein is preferably of current limiting type in order to make the cut-out suitable for very heavy fault conditions.

The overload protection device may be in series with the fuse as shown in the drawings or in certain cases may be in parallel therewith and in other cases may be in the secondary circuit of a current or voltage transformer, the primary circuit of the transformer including the fusible element.

What I claim is:

1. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in. that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device.

2. An electric cut-out comprising, in combination, a cartridge fuse ofcurrent limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from Which said overload protective device should be protected, and trip gear including a sprin loaded plunger and members for operating said plunger and positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device.

3. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive priorto the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear including a spring loaded rotatable element and members for operating said element and positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device.

4. An electric cut-out comprising, in combination, a casing, a cartridge fuse of current limiting type in said casing, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse in said casing, and including a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, strip gear in said casing and having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device, and a part connected with said trip gear and accessible externally of the casing.

5. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the car tridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior '7 to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, trip gear having members positioned in operative relation with said strikers for tripping .said gear upon operation of either said fuse or said overload device, and locking means to hold said trip gear against simple resetting after operation thereof.

6. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, trip gear having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device, and locking members to hold the striker operated by the cartridge fuse against simple resetting after operation of said cartridge fuse.

7. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, trip gear having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device, and locking means to hold the striker operated by the overload protection device against simple resetting after operation of said device.

8. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker cperatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse, said overload protection device including a trip coil with a displaceable element which provides a striker for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device.

9. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear including a catch to be displaced by operation of either of said strikers and a spring loaded element held against movement by said catch, displacement of said catch b a striker effecting release of said element to the influence of said spring.

10. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker o-peratively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear including a movable body to be displaced by displacement of either striker, a catch adapted to be displaced by movement of said body and a spring loaded element held against spring movement by said catch but released thereto when said body is displaced by a striker.

11. An electric cut-out comprising, in combination, a cartridge fuse of current limiting type, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse and a striker operatively connected for displacement by operation of said overload protection device, said overload protection devic being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridge fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fus in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, and trip gear including parallel links, each in proximity, respectively, to one of said strikers, a connecting rod between said links, a catch rigid with one of said links, and a spring loaded element held against spring movement by said catch so that displacement of either of said links by its striker will release said element to the influence of said spring.

12. An electric cut-out comprising, in combination, a casing, a cartridge fuse of current limiting type in said casing, a striker operatively connected for displacement by operation of said cartridge fuse immediately after fault clearance thereby, an overload protection device for said cartridge fuse in said casing and including a striker operatively connected for displacement by operation of said overload protection de-- vice, said overload protection device being adapted to be made effectively responsive by fault currents in that range of overloads against which the cartridge fuse is immune, said cartridg fuse being adapted to be made effectively responsive prior to the effective response of said overload protection device, which is slower acting than said cartridge fuse in response to fault currents in overload ranges of higher magnitudes from which said overload protective device should be protected, trip gear in said casing and having members positioned in operative relation with said strikers for tripping said gear upon operation of either said fuse or said overload device, and a switch in said casin to be operated by the tripping of said trip gear.

13. An electric cut-out comprising a current- REFERENCES CITED The following referenlce-s are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 327,499 Spalding Sept. 29, 1885 433,022 Noyes July 29, 1890 585,030 Harrington June 22, 1897 1,212,146 Nielsen Jan. 9, 1917 2,114,845 Kubik Apr. 19, 1938 2,306,153 Biermanns et a1. Dec. 22, 1942 2,330,690 Dannenberg Sept. 28, 1943 2,385,658 Strang et al. Sept. 25, 1945 FOREIGN PATENTS Number Country Date 2,733 Great Britain 1909 

